Jim DeMint, president of the Heritage Foundation / Evan Vucci, AP

by Alan Gomez USA TODAY, USA TODAY

by Alan Gomez USA TODAY, USA TODAY

The Heritage Foundation on Friday announced the resignation of Jason Richwine, the co-author of an immigration report who came under fire after his college dissertation claiming immigrants have lower IQ scores than the "white native population" went public.

"Jason Richwine let us know he's decided to resign from his position," the conservative think tank said in a statement. "He's no longer employed by Heritage."

Richwine was one of two co-authors on a report released Monday by Heritage that predicted a $6.3 trillion economic loss for the U.S. if a Senate immigration bill becomes law, legalizing the nation's 11 million unauthorized immigrants and bringing in more foreigners on work visas. The report was controversial, as even some Republicans, including Sen. Marco Rubio, R-Fla., argued it exaggerated the costs.

Two days later, Heritage came under intense criticism when it was revealed that Richwine's doctoral dissertation while he was at Harvard University -- titled "IQ and Immigration Policy" -- contended that the lower IQ of immigrants represented a mental divide that "is likely to persist over several generations."

"The consequences are a lack of socioeconomic assimilation among low-IQ immigrants groups, more underclass behavior, less social trust, and an increase in the proportion of unskilled workers in the American labor market," Richwine wrote. "Selecting high-IQ immigrants would ameliorate these problems in the U.S., while at the same time benefiting smart potential immigrants who lack educational access in their home countries."

Richwine's resignation was welcomed Friday by groups that had been protesting Heritage, but some said it has not gone far enough.

Zack Langway of the Center for Community Change, a social justice organization, said the resignation was "far too little and far too late." Langway's group formed an online petition on Thursday to get Jim DeMint, the former South Carolina senator who now heads the Heritage Foundation, to resign.

"It's the leadership and Jim DeMint himself who need to be held accountable. Jim DeMint needs to resign," Langway said.

After news of Richwine's college dissertation broke, Heritage defended its study, saying the data and methodology were sound. The statement said the authors did not rely on any of Richwine's previous work in analyzing the economic impact of immigrants on the U.S. economy.